Create JSON manifest file for directory

The following bash shell script was created for a very specific purpose; however due to licensing agreements the exact purpose cannot be disclosed as of yet. However, the techniques used here might prove useful to others striving to solve similar problems to that which I have just solved.

This script will inspect a directory of your choosing, and for each file in the directory, calculate the SHA-1 hash. A JSON file will then be created called "manifest.json" which lists each file along with its corresponding hash.

Usage: (Created and tested on a Mac)
From a Terminal prompt, enter:

bash manifestMaker.sh dir

where dir is the directory for which you want to create a manifest.

Script
Download the script from ManifestMaker, or see below for the source code. Remember to make the script executable.

#!/bin/bash

#script which generates a JSON file, which has as keys the filenames of all files in the given directory, and as values the SHA1 digest of the corresponding files

#check number of arguments is as expected
if [ $# -ne 1 ]
then
    echo "Need to provide directory on which to operate"
    exit 1
fi

src="$1"

#check directory exists
if [ ! -d $src ]
then
    echo "Directory $src does not exist"
    exit 2
fi

#change to specified directory
cd $src

#declare target output file
out="manifest.json"

#clean up first
rm $out
touch $out

#find the number of files - needed to know whether to put a "," at the end of each line or not
numFiles=$(ls | wc -l)

#start printing to the file
echo "{" >> $out

index=1
for file in *
do
#check if comma is needed at the end of the line
if [ "$index" -lt "$numFiles" ]
then
endLine=","
else
endLine=""
fi

#gives some unfriendly output formatting
digestFull=$(openssl sha1 $file)

#tidy up formatting to get actual value
digest=${digestFull#*= }

#print line to file
echo "    \"$file\" : \"$digest\"$endLine" >> $out

#increment our index
index=$[$index+1]

done

echo "}" >> $out